Production of IL-7 is increased in ovariectomized mice, but not RANKL mRNA expression by osteoblasts/stromal cells in bone, and IL-7 enhances generation of osteoclast precursors in vitro
Production of IL-7 is increased in ovariectomized mice, but not RANKL mRNA expression by osteoblasts/stromal cells in bone, and IL-7 enhances generation of osteoclast precursors in vitro
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DOI：
10.1007/s00774-006-0723-y
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发表时间：
2007-01-01
影响因子：
3.3
通讯作者：
Hakeda, Yoshiyuki
中科院分区：
文献类型：
--
作者：
Sato, Takuya;Watanabe, Ken;Hakeda, Yoshiyuki
由T和B谱系细胞产生的破骨细胞生成细胞因子和白细胞介素（IL）-7诱导的破骨细胞前体池大小的扩大已被认为在雌激素缺乏诱导的破骨细胞生成的加速中起重要作用。然而，在雌激素缺乏性骨质疏松症小鼠模型中，成骨细胞/基质细胞产生的RANKL增加对破骨细胞生成的贡献以及IL-7对破骨细胞前体生成的体外作用仍存在争议。因此，我们研究了小鼠卵巢切除术（OVX）对骨中RANKL、骨保护素（OPG）和IL-7产生的影响，以及IL-7对体外破骨细胞前体生成的影响。OVX未显著刺激全股骨RANKL和OPG mRNA的表达。由于骨骺，而不是股骨干（骨干）或骨髓，是破骨细胞生成的主要部位，因此特别分析股骨这些部位成骨细胞/基质细胞的mRNA表达是很重要的。因此，我们从骨髓无细胞骨骺、骨干和冲洗的骨髓中分离RNA并检测mRNA表达。结果显示，RANKL和OPG mRNA在股骨任何部位的表达均无显著变化。此外，OVX对从清除的骨髓细胞中分离的贴壁基质细胞的RANKL和OPG mRNA表达没有显著影响，但对非贴壁细胞部分中的B220（+）细胞的RANKL mRNA表达有刺激作用。另一方面，OVX增加了股骨中IL-7 mRNA的表达以及骨液中IL-7的浓度。通过剧烈搅拌切碎的整个长骨以释放紧密附着于骨表面的细胞而分离的未分级骨细胞的培养物中，但在克隆成骨细胞/基质细胞和冲洗出的骨髓细胞的共培养物中，IL-7刺激破骨细胞以及破骨细胞前体的产生。这些数据表明，成骨细胞/基质细胞产生的RANKL增加不太可能在雌激素缺乏小鼠破骨细胞生成加速中发挥核心作用，IL-7刺激破骨细胞前体生成，推测是通过IL-7对附着于骨的细胞而不是骨髓细胞群中所含细胞的作用。
Osteoclastogenic cytokines produced by T and B lineage cells and interleukin (IL)-7-induced expansion of the pool size of osteoclast precursors have been suggested to play an important role in acceleration of osteoclastogenesis induced by estrogen deficiency. However, the contribution of increased RANKL produced by osteoblasts/stromal cells to increase osteoclastogenesis in a mouse model of estrogen-deficient osteoporosis and in vitro effects of IL-7 on osteoclast precursor generation remain controversial. Thus, we investigated the effect of ovariectomy (OVX) of mice on production of RANKL, osteoprotegerin (OPG), and IL-7 in bone and the effect of IL-7 on osteoclast precursor generation in vitro. OVX did not significantly stimulate mRNA expressions of RANKL and OPG in whole femurs. Because the epiphysis, but not the femoral shaft (diaphysis) or bone marrow, is the main site of osteoclastogenesis, it is important to specifically analyze mRNA expression by osteoblasts/stromal cells at these parts of the femur. Therefore, we isolated RNA from bone marrow cell-free epiphysis, diaphysis, and flushed-out bone marrow and examined mRNA expression. The results showed no significant changes of RANKL and OPG mRNA expression in any part of the femur. In addition, OVX did not significantly affect RANKL and OPG mRNA expression by the adherent stromal cells isolated from flushed-out bone marrow cells but did stimulate RANKL mRNA expression by B220(+) cells in the nonadherent cell fraction. On the other hand, OVX increased IL-7 mRNA expression in the femur as well as IL-7 concentrations in bone fluid. In cultures of unfractionated bone cells isolated by vigorous agitation of minced whole long bones to release the cells tightly attached to the bone surfaces, but not in cocultures of clonal osteoblasts/stromal cells and flushed-out bone marrow cells, IL-7 stimulated generations of osteoclasts as well as osteoclast precursors. These data suggest that increased RANKL production by osteoblasts/stromal cells is unlikely to play a central role in acceleration of osteoclastogenesis in estrogen deficiency of mice and that IL-7 stimulates osteoclast precursor generation, presumably through an action of IL-7 on the cells attached to bone rather than on cells contained in the bone marrow cell population.